Heating of fluids



Oct. 5, 1937. 9 M. w. BARNES 2,094,913

HEATING OF FLUIDS Filed My 21, 1934 2 Sheets-Sheet l INVEN OR MARION W.RNES ORNEY I Oct. 5, 1937. M. w. BARNES 2,094,913

HEATING QF FLUIDS Filed May 21, 1934 2 Sheets-Sheet 2 INVEN OR 4 MARIONW. NES

AT ORNEY Y Patented Oct. 5, 1937 PATENT OFFICE HEATING 0F FLUIDS MarionW. Barnes, Chicago, Ill., assignor to Universal Oil Products Company,Chicago, 11]., a corporation of Delaware Application May 21, 1934,Serial No. 726,690

7 Claims.

This invention refers to an improved process and apparatus for theheating of continuous streams of fluids, and more particularly to theheating of hydrocarbon oils to the high temperatures required for theirpyrolytic conversion. The invention will be found especiallyadvantageous in the conversion or reforming of hydrocarbon oils ofrelatively low-boiling characteristics such as, for example,straight-run gasoline or other motor fuel of inferior antiknock value,naphtha, kerosene or kerosene distillate, pressure distillate, pressuredistillate bottoms and the like.

It has been proven by present practice that the most advantageous methodof converting relatively lowboiling hydrocarbon oils, of the type whichare practically entirely vaporized under the conversion conditions oftemperature and pressure to which they mustbe subjected for theproduction of motor fuel of high antiknock value, is to preheat the oilto near a cracking temperature, then rapidly heat it to or near themaximum conversion temperature desired and finally to maintain it at ornear the maximum temperature attained for a predetermined time.Following this treatment the stream of heated oil ordinarily is quicklycooled to a temperature at which no appreciable further conversion willoccur. By this method of treatment a definite control is exerted notonly over the temperature and pressure conditions to which the oil issubjected but also over the time during which the oil is subjected toappreciable conversion.

When this type or" treatment is employed in the type of furnacestructures ordinarily utilized in the conversion of hydrocarbon oils itnecessitates transferring the. stream of oil undergoing heating fromfluid conduits in one portion of the furnace to fluid 'conduits inanother rela means of connecting lines located entirely outside theiurnace or at least outside of the heating zone. In such casesdifliculties are often encountered in arranging the inlet and outletconnections to the furnace and the outside crossovers between difierentportions of the fluid conduit so that they do not interfere and, toavoid such interference, it is sometimes necessary to eliminate one ormore available tubes from the fluid conduit. The use of outsidecrossovers also necessitates the use of extra terminal fittings as wellas additional pipe sleeves in the furnace brick work. Connectionsbetween various portions of the fluid conduit located outside thefurnace or outside the heating zone also materially increase radiationlosses and the fire hazard is also increased on account of theadditional stresses in the fluid conduit, due to cooling in the outsidecrossovers.

The present invention offers an improved meth 0d and means for obtainingthe heating conditions most desirable for the conversion of lowboilinghydrocarbon oils in conventional furnace structures by passing the oilfirst through that portion of the fluid conduit located in the mildestheating zone of the furnace, wherein it is preheated to or near theconversion temperature, then passing the oil through that portion of thefluid conduit subjected to the most severe heating conditions, wherebyit is quickly heated to or near the maximum conversion temperaturedesired, and finally passing the stream of highly heated oil through aportion of the fluid conduit subjected to heating conditionsintermediate to those in the mildest and most severe heating zones ofthe furnace, whereby the oil is maintained at or near the maximumconversion temperature previously attained for a predetermined time. Inthe present invention this is accomplished without passing the oilthrough crossovers connecting the various portions of the fluid conduitlocated outside the furnace. Instead the lines'connecting the variousportions of the fluid conduit themselves comprise a portion of the fluidconduit and are located within the heating zone. This elimination ofconnecting lines or crossovers between various portions of the fluidconduit obviates all the disadvantages attendant with their use and thefeatures of the present invention provide other advantages not otherwiseobtainable which will be later more fully described.

The accompanying diagrammatic drawings illustrate two specific forms ofconventional furnace structures to which the features of the presentinvention are readily adaptable and demonstrates two specific methodsand means of adapting the ieatures'of the invention to each of thestructures illustrated.

Figs. 1 and 2 are cross-sectional elevations of what is ordinarilytermed a convection type furnace While Figs. 3 and 4 are sectionalelevations of a combination radiant and convection type furnace. Asomewhat different flow through the fluid conduit is indicated in eachof the four figures.

Referring particularly to Fig. 1, the main furnace structure comprisesside walls I and 2, a roof 3, a floor 4 and end walls which are notshown in the particular view here illustrated. The interior of thefurnace is divided by means of a partition or bridge wall 20 intocombustion zone 5 and'heating zone 6.

A combustible fuel-air mixture is supplied to combustion zone 5 of thefurnace through firing ports I by means of suitable burners, the tips ofwhich are indicated at 8 in the drawings. Combustion is entirely orsubstantially completed in combustion zone 5 and the hot combustiongases pass through openings 9 provided in the upper portion of wall 20into heating zone 6, passing downward therethrough over the fluidconduit provided in this zone to flue in from which they are directed toa suitable stack, not shown.

A fluid conduit ll comprising a plurality of superimposed, horizontallyparallel rows of horizontally disposed tubes I2 is located within theheating zone 6 and, in the case here illustrated, is divided into alower section I 3, an upper sec tion l4 anda central section l5. Sectionl3 comprises, in the case here illustrated, the lower three horizontalrows of tubes and the tube on the left hand of each of the succeeding(higher) six rows, while section it comprises the upper three horizontalrows of tubes and section I 5 comprises the remaining tubes in the 6centrally located rows of tubes. In the particular embodiment of theinvention here illustrated the oil to be treated enters the end tube ofthe lower row of section l3 adjacent side wall 2 of the furnace, flowingin series through adjacent tubes and adjacent rows of tubes in thissection by means of suitable return bends or headers disposedalternately on the far end and near end of the furnace, as indicated inthe drawings by the. dotted lines l6 and the full lines l1, rapectively.The oil then flows from bank l3 upward in series through adjacent tubesat the end of each horizontal row adjacent wall 20 to the uppermost rowof tubes in the huid conduit comprising the top row of section ll,passing in series through adjacent tubes of thisrowand in seriesthroughthe adjacent rows of this section of the fluid conduit, in a generaldownward direction, and then continuing from section It in seriesthrough adjacent tubes of the uppermost and-subsequent rows of tubes insection l5, being discharged-from the last tube of the. lowermost row ofthis section adjacent wall 2 of -the furnace to subsequent portions ofthe cracking system 'not pertinent to the present invention.

It will be apparent that section II of the fluid conduit, comprisingthat portion with which the hot products of combustion are firstcontacted, is subjected to the most severe heating conditions and, inaccordance with the features of the present invention, this is the zonewherein the stream of hydrocarbon oil undergoing treatment is quicklybrought to or near the maximum conversion temperature attained. Sectionl3 of the fluid conduit, with which the combustion gases are lastcontacted, prior to their removal from the furnace, is exposed to themildest heating conditions employed in the furnace and, in accordancewith the features of the present invention, comprises that section ofthe fluid conduit wherein the stream of hydrocarbon oil supplied tothe-furnace is heated, at a relatively slow rate, to or near a mildconversion temperature. Section l5 of the fluid conduit is subjected toheating conditions intermediate to those employed in sections II andparts of this furnace similar to the respective parts I to 20 inclusiveof Fig. 1.

In Fig. 2 the flow of oil through section H of the furnace is reversedto that in section II of Fig. 1 so that the flow of oil in both thepreheating section of the furnace and in the section wherein the oil isbrought to or near the maximum conversion temperature is in a generaldirection counter-current to the flow of combustion gases throughheating zone 6' while the flow of oil through the soaking section 15',wherein it is maintained at or near the maximum conversion temperaturepreviously attained for a predetermined time, is in a general directionconcurrent to the flow of combustion gases through heating zone 6'.

It is, of course, within the scope of the invention to utilize anydesired number of tubes and any desired number of rows of tubes in eachsection of the furnace and it is evident that the flow arrangementillustrated in Figs. 1 and 2 may be altered, when desired, to give moreor fewer tubes or rows of tubes in any of the sections I3, I4 and I5 or13', I4 and i5' without changing the total number of tubes in the fluidconduit. These details may be altered to suit the requirements of theparticular oil undergoing treatment to obtain the desired results andshould not be considered as limitations to the invention.

Referring now to Fig. 3, the main furnace structure here illustrated.comprises side walls 2| and 22, 'a roof 23, a floor 24 and end wallswhich are not illustrated in this particular view of the furnace. Theinterior. of the furnaceis divided by means of bridge wall 35' into acombustion and heating zone 25 and a convection heating zone 26.

Combustible fuel and air are supplied to the combustion zone, in thecase here illustrated, through fli'ing tunnels such as indicated, forexample, at 21; fuel of any suitable form, together with a regulatedportion or all of the air required for combustion, being supplied bymeans of a suitable burner 28 through combustion compartment 29 of thefiring tunnels, while regulated quantities of additional air may besupplied to the conbustion zone through ducts 30 located above andbeneath combustion compartment 29 of the flring tunnels.

The total fluid conduit, in the case here illustrated, comprises aplurality of horizontally parallel rows of horizontally disposed tubes32 located within fluid heating zone 26 of the furnace, two verticallyparallel rows of horizontally disposed tubes 32 located adjacent theupper portion of the side wall 22 of the furnace and two horizontallyparallel rows of horizontally disposed tubes 32 located adjacent theroof 23 of the furnace. wall 22 as well as the upper row or upper tworows of tubes in the convection heating zone receive an appreciablequantity of radiant heat f romthe materials undergoing combustion in thefurnace and the hot refractory walls of the furnace, while the remainingtubes in the convection The tubes adjacent roof 23 and side.

heating zone receive primarily convection heat by contact with the hotcombustion gases which pass from combustion zone 25 over bridge wall 36and downward through convection heating zone 26 to flue 3|, fromwhichthey pass to a suitable stack, not illustrated.

Section 33 of the fluid conduit, comprising,

in the case illustrated, the lowermost rbws of tubes in the convectionheating zone, is located in the mildest heating zone of the furnace andcomprises the preheating section to which the oil to be subjected toconversion is supplied and passed in series through adjacent tubes ineach row and through adjacent rows of tubes in a general upwarddirection, counter-current to the flow of combustion gases, whereby itis preheated to or near a. mild conversion temperature. The oil thenpasses in series through the end tubes adjacent bridge wall 36 of eachof the remaining rows of tubes in the convection heating zone to theuppermost row of tubes in the convection heating zone. Section 34 of thefluid conduit, comprising the uppermost row of tubes in the convectionheating zone, the two rows of vertical tubes adjacent the upper portionof wall 22 and the two rows of tubes adjacent the roof of the furnace;is subjected to the most severe heating conditions employed in thefurnace and comprises that portion of the fluid conduit wherein thepreheated oil is brought rapidly to or near 'the desired maximumconversion temperature.

The oil flows through this section of the furnace, in the case hereillustrated, first in series through adjacent tubes of the upperhorizontal row in the convection heating zone, then in series throughadjacent tubes of the exposed vertical row along the upper portion ofwall 22, then in series through adjacent tubes of the exposed rowadjacent roof 23, then in series through adjacent tubes of the shieldedrow adjacent roof 23 and finally through the shielded row of tubesadjacent wall 22 to the second horizontal row of tubes from the topof-convection heating zone 26. Section 35 of the fluid conduit,comprising the remaining tubes in the 8 horizontal rows of tubesimmediately beneath the uppermost row of tubes in convection heatingzone 26, is exposed to heating conditions intermedate to those employedin sections 33 and 34 of the fluid conduit and section 35 comprises thesoaking section wherein the treatment of highly heated hydrocarbon oilfrom section 34 is maintained at or near the maximum conversiontemperature previously attained for a predetermined time. The oil flowsin series through adjacent tubes in each row and through adjacent rowsof tubes of section 35, in a general direction concurrent to the flow ofcombustion gases through convection heating zone 26 and is dischargedfrom the furnace from the last tube of this section adjacent wall 22.

' Referring now to Fig. 4, the furnace structure except for the specificflow arrangement shown, is the same as that illustrated in Fig. 3. Thereference numbers 2| and 36 inclusive in Fig. 4 designate the same partsof the furnace as the respective reference numbers 2| to 36 inclusive inFig. 3. I

.In Fig. 4 the direction of flow through-section 34' of the fluidconduit is reversed to that through section 34 in Fig. 3. This isaccomplished, in the case illustrated, by eliminating one row of tubesin preheating section 33 and adding a row of. tubes to soaking section35' The preheated oil from section 33' passes upward in series throughadjacent end tubes next to side wall 22' of each horizontal row abovethe fifth row of tubes from the bottom in the convection heating zone,entering'the shielded row of vertical side wall tubes adjacent the upperportion of wall 22' flowing in series through adjacent tubes of this rowand the shielded row of roof tubes, then through the exposed row of rooftubes and the exposed row of wall tubes and through the top row of tubesin convection heating zone 26, passing therefrom to the soaking section35' wherein the stream of highly heated oil flows in series throughadjacent tubes of each row and through successive lower rows of tubes toand through the fifth row from the bottom from which it is dischargedfrom the furnace.

With the flow arrangement illustrated in Fig. 4 a progressive rate ofheating may be obtained throughout substantially the entire length ofsection 34 of the fluid conduit, wherein the oil is brought quickly toor near the maximum desired conversion temperature, the generaldirection of flow of the oil through preheating section 33' beingcounter-current to the direction of flow of the combustion gases throughconvection heating zone 26 while the direction of flow of the oilthrough the soaking section 35 is concurrent to the flow of combustiongases through the convection heating zone.

It will be noted in connection with the foregoing description and theaccompanying drawings that the method and means employed in thepresentinvention for connecting the various portions of the fluid conduiteliminates sudden changes in the heating condition to which the oil issubjected. For example, in all of the cases illustrated, the stream ofoil transferred from a relatively cool to a relatively hot zone of thefurnace is passed through successive zones of progressively increasingtemperatures from the relatively cool to the relatively hot zone and,vice versa, the oil transferred from a relatively cool to a relativelyhot zone of the furnace flows through successive zones of progressivelydecreasing temperatures from the relatively hot to the relatively coolzone. The advantages of this feature of the invention will be readilyapparent to those skilled in the art related but additional to theadvantages obtained by the elimination of connecting lines betweenvarious portions of the fluid conduit located outside the heating zone.

I claim as my invention:

1. A means of heating a continuous stream of fluid which comprises,. incombination, a tube bank comprising a plurality of superimposed,horizontally parallel rows of horizontally disposed tubes,'means forpassing hot combustion gases downwardly over said tube bank, anothertube bank comprising a row of tubes exposed to direct radiant heat and arow of tubes exposed to shielded radiant heat, means for passing thestream of fiuid to be heated first through several rows of tubes in thelowermost portion of the first mentioned tube bank, then throughadjacent end tubes in successively higher rows of the first mentionedtube bank to the second mentioned tube bank, then through the secondmentioned tube bank and finally through the remaining rows of tubes inthe first mentioned tube bank.

2. In combination with a furnace, fluid heating means in the furnacecomprising a plurality of serially connected horizontal tubes in theupper rows of horizontal tubes positioned in the furnace intermediatesaid plurality of tubes and the first-mentioned set of rows of tubes,and means connecting the first-mentioned set of rows of tubes in thelower portion of the furnace with said plurality of tubes in the upperportion of the furnace, said means comprising adjacent end tubes of therows of said additional set, the remaining tubes of said additional setbeing connected with said plurality of tubes in the upper portion of thefurnace.

3. In combination with a furnace, fluid heating means in the furnacecomprising a first and a second set of vertically. spaced, horizontalrows of serially connected horizontal tubes disposed respectively in theupper and lower portions of the furnace, an additional set of verticallyspaced,

horizontal rows of tubes disposed in the furnace intermediate said firstand second sets, and means connecting said first and second setscomprising adjacent end tubes of said additional set, the remainingtubes of said additional set being connected with the tubes of saidfirst set.

4. In combination with a furnace, fluid heating means in the furnacecomprising a first and a second set of vertically spaced, horizontalrows of serially connected horizontal tubes disposed respectively in theupper and lower portions of the furnace, an additional set of verticallyspaced, horizontal rows of tubes disposed in the furnace intermediatesaid first and second sets, means for passingcombustion gasm downwardlythrough the furnace over said fiuid heating means, and means connectingsaid first and second sets comprising adjacent end tubes of saidadditional set, the remaining tubes of said additional set beingconnected with the tubes of said first set.

5. In a furnace having a combustion zone and a convection heating zonethrough which combustion gases from the combustion zone are passed, thecombination of a plurality of serially connected tubes in the combustionzone, a set of vertically spaced, horizontal rows of serially connectedhorizontal tubes in the upper portion of the convection zone andconnected to the tubes in the combustion zone, another set of verticallyspaced, horizontal rows of serially connected horizontal tubes in thelower portion of the convection zone, and means for connecting thelastnamed set of rows of tubes with the tubes in the combustion zonecomprising a plurality of serially connected, vertically spaced,horizontal tubes disposed in the convection zone, each of the last namedtubes being in horizontal alignment with 'a row of said set in the upperportion of the convection zone.

6. In a furnace having a combustion zone and a convection heating zonethrough which combustion gases from the combustion zone are passedfthecombination of a. plurality of serially connected, radiantly heatedtubes in the upper portion of the combustion zone at a higher level inthe furnace than the upper portion of the convection zone and out of themain path of combustion gases from the combustion zone to the convectionzone, a set of vertically spaced,

' horizontal rows of serially connected horizontal tubes in the upperportion of the convection zone, connecting means between said set ofrows of tubes, and the tubes in the combustion zone and comprising aplurality of serially connected, vertically spaced, horizontal tubesdisposed in the furnace, another set of vertically spaced, horizontalrows of serially connected horizontal tubes in the lower portion of theconvection zone, and

means for connecting the last-named set of rows of tubes with the tubesin the combustion zone comprising a plurality of serially connected,vertically spaced, horizontal tubes disposed in the convection zone,each of the last named tubes being in horizontal alignment with a row ofsaid forming a connection between said sets of serially connected tubesand the remaining tubes of said rows being serially connected to providecontinuous fluid flow through said remaining tubes.

MARION W. BARNES.

